Green Mountain’s Precision .300 BLK AR-15 Launch Tube

We convert our AR to a sub-3/4-MOA-accurate.300 AAC Blackout for deer season

Here’s our completed .300 BLK rifle—wearing a Nikon M-.300 BLK 1.5-6×42 (with a .300-BLK-specific BDC reticle) in an FDE-colored American Defense AD-Delta QD mount—ready to get down ‘n dirty in the deer woods. Read on to see how we did it.The key ingredient in our .300 BLK conversion was this 4150-steel, 16-inch, precision-rifled Green Mountain Rifle Barrel Co. launch tube. You can order yours online at www.gmriflebarrel.com.

Along with the .300 BLK, Green Mountain also offers AR-15 barrels in 9mm, 5.56mm, .223 Wylde, and 7.62x39mm chamberings.

The .300 BLK offering features exterior fluting, a chrome-lined chamber and bore, and 5/8×24 muzzle threads as standard equipment.

The first step to replacing your barrel is to remove whatever device is threaded to the muzzle using (almost always) a 3/4-inch wrench. Daemon Defense uses the excellent CMMG SV muzzle brake, and we’ll be installing the same component (only with the requisite .300 BLK dimensions) on our new barrel.

We’re blessed with a local source of premium AR barrels: Green Mountain Rifle Barrel Co. located right here in Conway, New Hampshire. Green Mountain Rifle Barrel Co. was founded in 1976 by friend, Branch Meanley, with machinery he custom made or modified to turn his vision of the perfect rifle barrel into reality. Long-time employee-turned-current owner Rick Sanborn took the helm of operations in 2013, and has been instrumental in turning Green Mountain Rifle Barrel Co. into what is currently the largest barrel manufacturer in the country. Blessed, yes, but we’re also extremely proud to have them as a part of our local economy.

The next step is to liberate your rifle of its handguard. This procedure varies widely based on manufacturer, but with the particular Keymod rail fitted to this rifle, it simply required removal of three Allen-head set screws and unscrewing the forend from the threaded barrel nut.